Help - Yanmar 3GM30F Starting problem?

[BobnLesley]

Our Yanmar has so far run perfectly, no smoke, ample power and starts in 2-3 seconds of pressing the button; we've been sailing Med, Caribbean, US East Coast, so temperatures generally 20C+, often to 30C.

We've now got caught by the snow/ice storms effecting the US East Coast and so temperatures are in the -2C to 10C range and whilst the engine's as good as ever once it's running, starting has become scarily difficult.

Despite having a brand new 850 CCA starting battery fitted, it won't spin the engine on its own, even with one of the decompressor lifters open; if we connect the domestic bank in too - not something I'm comfortable with as they're Trojan deep-cycle batteries - the engine then spins OK, but often takes 20 seconds plus to fire-up - again we're starting with one decompressor open.

I've checked through the wiring and get solid (13V +/-) readings everywhere and can't find any loose connections; the circuit has a relay fitted, so we're no trying to get all those amps out to the ignition switch and back.

Any suggestions where I should look next?

 

[sailorman]

what grade of oil are you using,is there a cold start throttle setting

 

[Sandyman]

Oil viscosity ?

 

[mtb]

Oil viscosity ?

plus 1
Ive had this many times with old engines

 

[BobnLesley]

I don't think so. We were running on SAE 30 whilst in the Caribbean, but since we got to Maine in the summer, we changed to Shell Rotella T, which is a 15 - 40.

Being the USA, they 'spike' their diesel with ethanol which I'm sure doesn't help, but since we got the starting difficulties, we've been doing the fuel with Stabrite's 'Startron Diesel Fuel Enzyme Treatment'; it was 'recommended' but doesn't appear to have made any difference.

 

[sailorman]

I don't think so. We were running on SAE 30 whilst in the Caribbean, but since we got to Maine in the summer, we changed to Shell Rotella T, which is a 15 - 40.

Being the USA, they 'spike' their diesel with ethanol which I'm sure doesn't help, but since we got the starting difficulties, we've been doing the fuel with Stabrite's 'Startron Diesel Fuel Enzyme Treatment'; it was 'recommended' but doesn't appear to have made any difference.

the 15/40 would have been better in the hotter climate. try a thinner viscosity oil even the straight 30.
what about the cold start setting

 

[Sandyman]

If you have the facilities try putting a heater under your donk for a few hours then try starting it. If no problem then defo the oil.

 

[HunterWanderer]

Sounds like it could be the starter motor. Perhaps a stiff bearing.

 

[BobnLesley]

"...what about the cold start setting..."

The Yanmar doesn't have one, other than the ability to de-compress the cylinders individually; there are no glow-plus/pre-heaters fitted, the only advice I received (on the YBW Forum) for 'cold-start' technique was to "give it full throttle, but back-off the moment it catches."

 

[lw395]

The problem sounds like the engine is not turning over fast enough?
First, check the batteries are fully charged, >12.5V.
I would first get a DC clamp ammeter and see what current the starter is pulling.
If it's less than 100A, either the battery is weak or the wiring is bad or the starter is sick.
Get a voltmeter with a max/min function. put it on the battery, crank the motor.

If the battery stays up at 11V or more, there is probably a problem with the wiring. The motor is not drawing the current it should.
If the volts are dragged down to say 8 V, then I'd guess the engine is stiff to turn, or the starter is shot.

 

[garvellachs]

"...what about the cold start setting..."

The Yanmar doesn't have one, other than the ability to de-compress the cylinders individually; there are no glow-plus/pre-heaters fitted, the only advice I received (on the YBW Forum) for 'cold-start' technique was to "give it full throttle, but back-off the moment it catches."

I think the cold start setting really is to give it full throttle - I think that's in the manual? I recall reading that this sets the engine differently for the short period until it starts.

 

[vyv_cox]

I have experienced similar problems with Bosch starter motors on road vehicles - started fine in summer but not in winter. When the pre-engage solenoid throws forward a short length of copper bridges two copper terminals, sending power to the motor. This crude arrangement tends to become pitted, allowing only a proportion of the current to flow. Dressing the terminals up with a file will fix it, assuming the later ones disassemble as the older ones did.

On road vehicles the braided cable between the solenoid and the motor becomes corroded. I have seen this once on the same motor on a fairly large Volvo in a Westerly yacht. Could be worth checking.

 

[BobnLesley]

Thanks for the input. I replaced the starter this morning with the spare one and it started OK using just the starter battery, though the one I took off felt equally smooth running to the one I've replaced it with; also the temperature's jumped from 35-40F to 65F overnight, so whether it's changing the motor or the world just being warmer, I have yet to discern; I'll get the removed motr checked-out by an expert at the first opportunity; thanks again, Bob.